Engine control systems having an engine automatic stop-and-restart function, in other words, an idle reduction function, are known. The engine automatic stop-and-restart function is designed to, in response to a driver's engine stop operation, such as an operation of a brake pedal, stop the burning of air-fuel mixture in each cylinder so as to automatically stop the internal combustion engine. After the stop of the internal combustion engine, the engine automatic stop-and-restart function is designed to cause, in response to a driver's operation to restart the vehicle, such as an operation of an accelerator pedal, a starter to crank the internal combustion engine and thereafter to start the supply of fuel to the internal combustion engine, thus restarting the internal combustion engine.
Various types of techniques are provided for the idle reduction function. For example, the first technique disclosed in, for example, Japanese Patent Application Publication, referred to as “first publication”, is designed to, after the internal combustion engine (referred to simply as “engine”) has been automatically restarted, disable to carry out the next automatic stop of the engine until the vehicle speed is equal to or higher than a preset speed (for example, 15 km/h).
This first technique restricts frequent repetitions of the automatic stop and restart of the engine while, for example, the vehicle is running at a low speed due to traffic jam and the like.
In addition, the second technique disclosed in, for example, U.S. Pat. No. 6,702,718, referred to as “second publication”, corresponding to Japanese Patent Application Publication NO. 2002-221059 is designed to carry out the idle reduction function during the vehicle being decelerated.
Specifically, the second technique is designed to deter mine that at least one of predetermined engine automatic stop conditions is met when the vehicle speed is reduced with reduction in the rotational speed of the engine due to cut off the supply of fuel to the engine, and to automatically stop the engine in response to the determination. This second technique reduces the opportunities to operate the engine in idle, thus reducing fuel consumption.
During the engine being automatically stopped, when the accelerator pedal is operated so that the vehicle is accelerated, the second technique determines that at least one of predetermined engine restart conditions is met. Thus, the second technique causes the starter to crank the engine and thereafter to start the supply of fuel to the engine, thus restarting the engine.